Articles | Volume 12, issue 11
Nat. Hazards Earth Syst. Sci., 12, 3255–3267, 2012

Special issue: Marine and lake paleoseismology

Nat. Hazards Earth Syst. Sci., 12, 3255–3267, 2012

Research article 07 Nov 2012

Research article | 07 Nov 2012

Acoustic and seismic imaging of the Adra Fault (NE Alboran Sea): in search of the source of the 1910 Adra earthquake

E. Gràcia1,2, R. Bartolome1,2, C. Lo Iacono1,2, X. Moreno1,3, D. Stich4, J. J. Martínez-Diaz5, G. Bozzano6, S. Martínez-Loriente1,2, H. Perea1,2, S. Diez1, E. Masana3, J. J. Dañobeitia1,2, O. Tello7, J. L. Sanz7, E. Carreño8, and EVENT-SHELF Team* E. Gràcia et al.
  • 1Unitat de Tecnologia Marina – CSIC, CMIMA, Pg. Marítim de la Barceloneta 37–49, 08003 Barcelona, Spain
  • 2Institut de Ciències del Mar – CSIC, CMIMA, Pg. Marítim de la Barceloneta 37–49, 08003 Barcelona, Spain
  • 3RISKNAT, Dpt. Geodinàmica i Geofísica, Universitat de Barcelona, Martí i Franquès s/n, 08028 Barcelona, Spain
  • 4Instituto Andaluz de Geofísica (IAG), Univ. Granada, 18071 Granada, Spain
  • 5Instituto de Geociencias UCM, CSIC, Dpto. Geodinámica, Facultad de Ciencias Geológicas, Universidad Complutense, 28004 Madrid, Spain
  • 6Servicio de Hidrografía Naval, Av. Montes de Oca 2124, C1270ABV Buenos Aires, Argentina
  • 7Instituto Español de Oceanografía, Corazón de María 8, 28002 Madrid, Spain
  • 8Red Sísmica Nacional, Instituto Geográfico Nacional, c/ General Ibáñez Ibero, 3, 28003 Madrid, Spain
  • *M. Farran (ICM-CSIC), E. Andara (IGME), S. Pérez and M. J. Román Alpiste (UG)

Abstract. Recently acquired swath-bathymetry data and high-resolution seismic reflection profiles offshore Adra (Almería, Spain) reveal the surficial expression of a NW–SE trending 20 km-long fault, which we termed the Adra Fault. Seismic imaging across the structure depicts a sub-vertical fault reaching the seafloor surface and slightly dipping to the NE showing an along-axis structural variability. Our new data suggest normal displacement of the uppermost units with probably a lateral component. Radiocarbon dating of a gravity core located in the area indicates that seafloor sediments are of Holocene age, suggesting present-day tectonic activity. The NE Alboran Sea area is characterized by significant low-magnitude earthquakes and by historical records of moderate magnitude, such as the Mw = 6.1 1910 Adra Earthquake. The location, dimension and kinematics of the Adra Fault agree with the fault solution and magnitude of the 1910 Adra Earthquake, whose moment tensor analysis indicates normal-dextral motion. The fault seismic parameters indicate that the Adra Fault is a potential source of large magnitude (Mw ≤ 6.5) earthquakes, which represents an unreported seismic hazard for the neighbouring coastal areas.